1. Field of the Invention
The present invention relates to a member for resiliently supporting the friction plate of a brake for an automatic transmission for a vehicle.
2. Description of the Related art
A planetary gear mechanism includes a plurality of frictionally engaging elements. In a planetary gear mechanism, a brake causes a rotating member to frictionally engage the automatic transmission case, as required. As shown in FIG. 3, this frictional engagement is effected between a friction plate spline-engaged with a rotating member 14 and a separator plate 20 spline-engaged with an automatic transmission case 3. The automatic transmission case 3 is provided with a breather opening 32 serving to allow the space inside the case 3 to communicate with the atmospheric air. However, because one of the chambers of the automatic transmission partitioned by a brake (e.g. B0) does not communicate with the breather opening 32 and is hermetically closed, the temperature of hydraulic oil inside that case chamber can rise owing to the rotation of the rotating member. This can cause the air pressure within the case chamber to rise, thereby possibly hampering proper flow of the oil. For that reason, a gap 21 is provided between the terminus of each of a plurality of projections 20a (FIG. 1), provided on an outer peripheral portion of the separator plate 20 of the brake B0, and the bottom of each of a plurality of recesses 3a formed in the interior of the automatic transmission case 3 and into which the projections 20a of the separator plate 20 are respectively inserted. These air gaps 21 communicate with the space in the chamber of the automatic transmission case 3 partitioned axially via the brake B0 and further communicate with the atmospheric air via the breather opening 32.
In addition, if the gaps 21 are present, the friction plate 22 rotates due to the rotation of the rotating member 14, which in turn causes the separator plate 20 to move due to frictional contact with the friction plate 22. Hence, the separator plate 20 strikes the automatic transmission case 3, resulting in interference noise between the case 3 and the separator plate 20. To suppress this interference noise, a leaf spring is usually attached to the wall surface of the case 3 in each gap 21 in such a manner that the longitudinal direction of the leaf spring is aligned with the longitudinal direction of the gap 21 (refer to Japanese Patent Application Laid-Open No. 46324/1990).
However, as for the space inside the transmission case 3 partitioned into two chambers 2E, 2C by the rotating member 14 and the brake B0, if there is a large difference in capacity between the space 2E provided with the breather opening 32 and the space constituted by a transmission mechanism chamber 2C, unless sufficient breathing is provided by the gaps 21, there is a possibility that air will be forced through oil within the case 3 due to the difference in internal pressure based on the difference in volume as between the two chambers.
However, if the gap 21 is enlarged to increase pressure equalizing air flow between the two chambers, the leaf spring which is conventionally used for preventing clattering noise cannot serve its purpose. Accordingly, a large-sized, rigid, and resilient leaf spring becomes necessary in order to bridge the distance between the bottoms of recesses 3a on the inner peripheral surface of the automatic transmission case 3 and the tips of projections 20a on the outer peripheral surface of the separator leaf 20. In other words, the weight of a leaf spring necessary to perform its intended function becomes larger. In addition, if the size of the leaf spring, which is disposed with its longest dimension arranged parallel to the axis of the rotating shaft of the transmission, is increased, the increased size of the leaf spring blocks the aforementioned gap 21, thereby reducing the breathing capacity of the gap 21. That is, as shown in FIG. 6 which is a fragmentary cross-sectional view of the transmission, a curled portion of a leaf spring 24, which extends radially of the rotating shaft of the transmission, blocks the gap 21. It should be noted that the view of the leaf spring 24 alone which is shown in FIG. 6 is not a sectional view but an external view looking into the gap 21. Furthermore, in order to effectively accommodate such an enlarged leaf spring, the space 21 must be axially extended